Though soil nutrient availability and disturbance are critical drivers of plant communities in tropical forest understories, the degrees to which soil nutrients and disturbance drive plant associated microbial communities are poorly understood. Here, we test whether soil nutrients, host species, and disturbance regime structure foliar bacterial endophyte communities in a tropical forest in Panama where bacteria are abundant and diverse. We test the following hypotheses: 1) Bacterial endophyte richness, diversity, and community composition vary substantially among coexisting plant species and 2) soil nutrient availability (N, P, K). Furthermore, we hypothesize that 3) disturbance (e.g., antibiotic applications) cause substantial changes in endophyte community compositions. To address these hypotheses, we use high-throughput sequencing to characterize bacterial endophyte community composition among seedling leaves of five co-occurring woody species (Alseis blackiana, Desmopsis panamensis, Heisteria concinna, Sorocea affinis, and Tetragastris panamensis) nested in a long-term experimental manipulation of soil nutrients (N, P, and K). To simulate a disturbance regime on endophyte communities, we applied commercial antibiotics to a subset of Tetragastris seedlings in the field for almost three years.
Results/Conclusions
While endophyte richness, diversity, and community composition differed among plant host species and soil nutrient additions, together plant hosts and soil nutrient additions accounted for <10% of the variation in endophyte community composition. For Tetragastris, no nutrient addition combinations caused a change in endophyte community structure, however antibiotic applications increased endophyte richness by 57% and diversity by 126%. While our data support all three hypotheses to a certain degree, we suggest that plant host species are not as important as previously thought in structuring endophyte communities. Moreover, we suggest that disturbance is more important than soil nutrients, a critical driver of plant community dynamics, in structuring plant microbiomes.